With his crew chief back after serving a two-week suspension, Brad Keselowski snapped his mini-drought by placing fifth in the FedEx 400 at Dover International Speedway.
It was the defending Sprint Cup champion's first top 10 since a sixth at Kansas on April 21.
The euphoria over the good run Sunday was short-lived, however, as Keselowski's No. 2 Ford failed post-race inspection after NASCAR inspectors found the front of the car to be too low.
Penalties are likely forthcoming and typically announced on Tuesdays.
Martin Truex Jr. had a similar breach after a runner-up finish at Texas and was docked six points. His crew chief was also fined $25,000 and placed on probation until June 5.
The circumstances in this case are different. Dover is the second time this season Penske Racing has committed a rules infraction.
During prerace inspection at Texas, officials confiscated unapproved suspension parts from the team. NASCAR later stripped Keselowski of 25 points and suspended crew chief Paul Wolfe, car chief Jerry Kelley, engineer Brian Wilson and Penske competition director Travis Geisler six races. The suspensions were later reduced to two races on appeal.
But because Wolfe is on probation until the end of the year, it is unclear whether that will impact any subsequent penalties.